(1) Summary: the goal of this project is to define the mechanisms by which input from the retina and LGN directs the postnatal development of orientation selectivity in the ferret. This will be accomplished by (1) blocking retinal output with tetrodotoxin during development and (2) preventing axons from the LGN from reaching the cortex by destroying the cortical subplate. Following recovery from these manipulations,their effetcts will be assessed by optical and single unit recordings in the adult accompanied by an assessment of alterations in the cortical anatomy. The goal will be to describe disruptions in the normal corresponding physiological changes in neural response properties.